It is
I actually watched the replay and have some few things to say:
1. If you are going to build mass fiends, build in this order:
-graveyard
-crypt
-zig
-altar
2. You shouldn't stand still so much. If you have nothing to do, go creep or do a hit-and-run attack at your opponents base just to see what he is doing.
3. Dont upgrade all your ziggurats into spirit towers
It's noobish and totally useless. You could build 1 nerubian tower in the begining if you are going for a "weak" start.
4. You should build AT LEAST 1 obsidian gargoyle in the slaughterhouse to heal your army.
5. Be quicker and learn how to micro.
6. Playing against the computer is useless, get on Bnet :wavey
Btw.. the best (and fastest) way to beat computer insane is a simple early ghoul rush.
I thought of something else too, but i forgot it. It annnoys me right now.